Do artificial velocity refuges mitigate the physiological and behavioural consequences of hydropeaking on a freshwater Iberian cyprinid?. Issue 7 (2nd May 2018) - Costa, M.J.
Abstract: The rapid flow fluctuations experienced downstream of hydropeaking facilities can alter the river hydromorphology. Given the dependence of riverine fish on physical habitat, those alterations have the potential to change the physiology and behaviour of fish. We assessed whether artificial velocity refuges mitigated the physiological and behavioural consequences of hydropeaking for the Iberian barbel ( Lucio barbus bocagei ). Hydropeaking trials were conducted in an indoor flume equipped with deflectors that created low flow velocity areas to serve as refuges. The FLOW‐3D was used to obtain detailed characterizations of the different velocity fields, which facilitated the interpretation of fish responses. Changes in flow magnitude and duration triggered stress responses, demonstrated by the increased blood glucose levels in the single up‐ramping event for 60 L s −1 and in the step up‐ramping event. Fish tended to seek out velocity refuges to avoid higher flow velocities and harsh hydraulic conditions at peak flows, and during the longer events. The movement behaviour frequency increased when fish were subjected to the highest peak flow (60 L s −1 ), particularly the individual sprints and the drifts. For the base flow (7 L s −1 ) and the lowest peak flow (20 L s −1 ) conditions, fish swam freely in the flume, whereas in the harshest hydraulic conditions they showed more difficulty in finding velocity refuges. This research presents a novel approach by combining physiology and behavioural observations with hydraulic modelling to assess the extent to which artificial flow refuges mitigate the consequences of hydropeaking. Our work serves as a model approach for future mitigation studies for fish in hydropeaking rivers.